 # How would you calculate the average atomic mass of copper if 69.2% of copper has a mass of 62.93 amu and 30.8% has a mass of 64.93 amu?

Cu-63 and Cu-65 are the isotopes of Copper.Cu-63 and Cu-65, are used to study copper metabolism and gastrointestinal diseases. Cu-63 is used for production of medical radioisotope Zn-62 and can also be used for the production of Cu-64 which is used in cancer diagnosis and treatment. Cu-65 has also been proposed as a precursor for the (cyclotron) production of Cu-64.

## Solution

Given

The atomic mass of Cu63is 62.93 and relative abundance = 69.2%

The atomic mass of Cu65is 64.93 and relative abundance = 30.8%

Formula

The average atomic mass of an element is calculated by taking the weighted average of the atomic masses of its naturally-occurring isotopes.

avg. atomic mass
=∑ i (isotope i×abundancei)

The atomic masses of these two copper isotopes are 62.93 uand 64.93 u , respectively.

Therefore, relative atomic mass of Cu = (62.93×69.2)+(64.93×30.8) / 100

=63.546